A chemical method of incorporating copper into indium selenide thin-films has been
investigated, with the goal of creating a precursor structure for conversion into
CuInSe2 layers suitable for solar cell processing. The precursor and converted layers
have been investigated with scanning electron microscopy, x-ray diffraction, Raman
spectroscopy and x-ray photoelectron spectroscopy. From these measurements, the
incorporation of copper into the indium selenide layers is concluded to proceed by an
ion-exchange reaction. This reaction results in the formation of a precursor layer with
a graded compositional depth-profile containing the crystalline phases In2Se3 and
Cu2-xSe. Selenization of the precursor layer homogenises the composition and forms
chalcopyrite CuInSe2. These CuInSe2 layers exhibit a dense microstructure with
rough surface morphology, which is ascribed to a non-optimal selenization process.
Solar cells with the structure ZnO:Al/i-ZnO/CdS/CuInSe2/Mo/Glass have been
processed from the selenized layers and have exhibited efficiencies of up to 4% under
simulated AM1.5 illumination.